1. Field of the Invention
The present invention is directed to threshold gates. More specifically, the present invention is directed to a threshold gate having a variable threshold level related to the amplitude of an input signal applied to the threshold gate.
2. Description of the Prior Art
In the field of data handling and process control, communication is often required between two remotely located transceiver devices connected to a common communication cable. In such a system, communication between nearby transceiver devices results in a high received signal level while between widely separated transceiver devices a low received signal level is common. Whatever the received signal level, communication between transceiver devices is most reliable when the receiver's input signal transmission gate threshold level is set at approximately one-half, i.e., 50 percent, of the signal level on the cable regardless of the actual signal level. The problem of a varying input signal is ordinarily handled by utilizing an automatic gain control circuit in front of the transmission gate which arrangement prevents the transmission gate from being affected by the signal variations on the cable. However such a prior art solution involves the use of a nonlinear device in the gain control circuit in order to provide automatic gain control adjustments which non-linear devices can give rise to inaccuracies in the ultimate output signal from the transmission gate.